Rhododendron plant named ‘WALSNOWRUF’

ABSTRACT

A new and distinct variety of  Rhododendron  plant named ‘WALSNOWRUF’ which is characterized by compact mounding habit, glossy evergreen foliage, large double bright white flowers which are produced from early summer through early fall (July to September approximately), is disclosed.

Genus and species: Rhododendron kaempferi hybrid.

Variety denomination: ‘WALSNOWRUF’.

BACKGROUND OF THE NEW PLANT

The present invention relates to a new and distinct cultivar ofRhododendron, also commonly known as evergreen azalea, which is grown asan ornamental shrub for use in planted containers and in the garden andlandscape. The new cultivar is known botanically as Rhododendronkaempferi hybrid, and will be referred to hereinafter by the cultivarname ‘WALSNOWRUF’.

‘WALSNOWRUF’ arose and was selected from a long term breeding programcommenced by the inventor in 1993 or 1994. The aim of the breedingprogram was to develop one or more matched series of novel cultivars ofhardy evergreen azaleas with showy flowers, large open-faced singleflowers, and also heavily flowering double flower forms. Breedingcommenced with Azalea ‘Elsie Lee’ as one of the initial parents. Azalea‘Elsie Lee’ is a Shammarello hybrid, raised in Ohio in the 1960s andrenowned for its fertility and relative hardiness among evergreenazaleas. Although several Shammarello hybrids were patented in the 1960sand 1970s, the inventor believes that Azalea ‘Elsie Lee’ was unpatented.‘Elsie Lee’ bears light mauve-blue semi-double flowers.

Commencing in 1993 or 1994, many generations of deliberate hybrids wereraised, selecting promising parents from his collection of previousunnamed seedlings which had been raised during the breeding program. Theinventor selected ‘WALSNOWRUF’ in 2003 or 2004. The intermediate andimmediate parents of ‘WALSNOWRUF’ are unknown to the inventor and havenot been retained. Thus, no parental comparison information isavailable.

Asexual propagation of ‘WALSNOWRUF’ was first accomplished by theinventor in 2003 or 2004 using semi-ripe shoot cuttings. Since thattime, under careful observation, the distinguishing characteristics of‘WALSNOWRUF’ have been determined stable and uniform, and to reproducetrue to type in successive generations of asexual propagation viasemi-ripe shoot cuttings.

SUMMARY OF THE NEW VARIETY

The distinguishing characteristics of ‘WALSNOWRUF’ are listed below.‘WALSNOWRUF’ has not been tested under all possible conditions andphenotypic differences may be observed with variations in environmental,climatic, and cultural conditions.

-   -   1. Plants of ‘WALSNOWRUF’ exhibit a compact mounding growth        habit.    -   2. The foliage of ‘WALSNOWRUF’ is glossy evergreen in color.    -   3. ‘WALSNOWRUF’ bears large double flowers in a crisp white        color.    -   4. Plants of ‘WALSNOWRUF’ show good heat and humidity tolerance.    -   5. ‘WALSNOWRUF’ blooms profusely from April until June with        occasional flowers present through summer and into early fall.    -   6. After two years of growth, plants of ‘WALSNOWRUF’ are 25 cm        to 30 cm in height and 25 cm to 30 cm in width.    -   7. At maturity, 5 years, plants of ‘WALSNOWRUF’ are 30 cm to 40        cm in height and 30 cm to 40 cm in width.    -   8. ‘WALSNOWRUF’ prefers semi-shade in a moist, well drained,        slightly acidic growing media.    -   9. ‘WALSNOWRUF’ is suitable for use as a garden specimen,        landscape plants and as a container specimen.    -   10. ‘WALSNOWRUF’ is hardy to at least USDA Zone 7.

DESCRIPTION OF THE PHOTOGRAPHS

The accompanying color photographs illustrate the overall appearance of‘WALSNOWRUF’ showing the colors of its foliage and flowers as true as itis reasonably possible to obtain in colored reproductions of this type.Both photographs were taken in May 2013 from one-year old plants whichhave been grown outdoors in 3-liter containers in the inventor's nurseryin Arundel, West Sussex, United Kingdom.

FIG. 1 depicts a whole plant of ‘WALSNOWRUF’.

FIG. 2 depicts a close-up view of the flower of ‘WALSNOWRUF’.

BOTANICAL DESCRIPTION OF THE PLANT

The following is a detailed description of ‘WALSNOWRUF’. The observedplant was 2-years old and was growing out of doors in a 1-galloncontainer in Santa Barbara, Calif. where the botanical description wasmade in May 2014. The color determinations are in accordance with the2007 edition of The Colour Chart of the Royal Horticultural Society,London, England, except where general color terms of ordinary dictionarysignificance are used. Growing conditions are similar to those of otherRhododendron.

-   Botanical classification:    -   -   Family.—Ericaceae.        -   Genus.—Rhododendron.        -   Species.—kaempferi hybrid.        -   Cultivar.—‘WALSNOWRUF’.-   Parentage: Un-named seedlings raised during the breeding program;    parents not retained or described.-   Plant:    -   -   Commercial classification.—Perennial.        -   Common name.—Evergreen azalea.        -   Use.—Ornamental for container or landscape.        -   Cultural requirements.—Plant in partial shade and any            free-draining slightly acidic soil.        -   Particular pest resistance or susceptibility.—None observed.        -   Propagation method.—Semi-ripe cuttings without use of            rooting hormone.        -   Rooting system.—Fine and fibrous.        -   Time to initiate roots.—Roots begin to form after 5 to 8            weeks; a further 5 weeks are required for the plant to be            well-rooted.        -   Vigor.—Moderately vigorous; lateral branching is encouraged            by pinching.        -   Habit.—Low mound.        -   Dimensions after two years.—25 cm to 30 cm in height and 25            cm to 30 cm in width.        -   Dimensions after five years.—30 cm to 40 cm in height and 30            cm to 40 cm in width.        -   Hardiness.—USDA Zone 7.-   Stem:    -   -   Dimensions.—Length 1.5 cm (height of manual pinch); diameter            at base: 1 cm.        -   Shape.—Cylindrical.        -   Bark.—Rough, color 177A.        -   Number of branches.—12.-   Branches (current season extension growth):    -   -   Shape.—Cylindrical.        -   Surface.—Sparsely pubescent.        -   Dimensions.—Length: 18 cm to 20 cm, diameter 3 mm.        -   Color.—144B.        -   Internode length (range).—1.0 cm to 1.5 cm.-   Branches (previous year's growth):    -   -   Shape.—Cylindrical.        -   Dimensions.—Length: 15 cm to 20 cm, diameter 3 mm.        -   Color.—172A.        -   Bark surface.—Rough.        -   Internode length (range).—1.0 cm to 2.0 cm.-   Foliage:    -   -   Type.—Evergreen.        -   Leaf arrangement.—Alternate.        -   Leaf division.—Simple.        -   Leaf dimensions (average, fully developed).—6 cm in length            and 3 cm in width.        -   Leaf color (current season new growth, adaxial            surface).—141B.        -   Leaf color (current season new growth, abaxial            surface).—143C.        -   Leaf color (mature, previous year's growth, adaxial            surface).—136A.        -   Leaf color (mature, previous year's growth, abaxial            surface).—138A.        -   Leaf shape.—Elliptic, base cuneate, apex obtuse.        -   Leaf margin.—Ciliate, hairs fine, 1 mm, silver-gray 156D.        -   Leaf surface (both surfaces).—Smooth, glossy, sparsely            pubescent, hairs fine, 1 mm, silver-gray 156D.        -   Venation.—Pinnate, color 141B.        -   Petioles.—Dimensions: 5 mm in length, 1.5 mm to 2.0 mm in            width. Color: 144A.-   Inflorescence:    -   -   Inflorescence type.—Terminal.        -   Flower arrangement.—Flowers in groups of 8 to 12.        -   Flower aspect.—Upward or outward.        -   Form.—Rotate.        -   Inflorescence quantity.—Ranges between 3 and 5 per branch            and between 30 and 50 at peak of flowering.        -   Dimensions of inflorescence (average).—10 cm in diameter, 8            cm in depth.        -   Blooming season.—Early summer through early fall (July to            September approximately).        -   Lastingness of flowers (on the plant).—7 to 10 days.-   Bud:    -   -   Arrangement.—Borne in clusters of 8 to 12 buds; initially,            each bud is sheathed by a pair of modified leaf bracts which            fall away as the bud swells.        -   Bud shape.—Ovoid.        -   Dimensions (immediately prior to opening).—12 mm in length            and 10 mm in diameter.        -   Bracts (bud sheath).—Pair, each 18 mm in length, 15 mm in            width.        -   Bracts (bud sheath).—Shape cupped, texture paper-like, base            truncate, apex acute.        -   Bract color (adaxial surface).—Base 155C, becoming 142C and            142B at apex; in addition, dorsal (convex) surface 163A.        -   Bract color (abaxial surface.—Base 155C, becoming 142C and            142B at apex.        -   Bud color (as bracts fall away, as bud opens).—149D.        -   Sepals.—5 in number, fused at base.        -   Sepal color (both surfaces).—144A, surface pubescent, hairs            fine, 1 to 2 mm, silver-gray 156D.        -   Sepal dimensions.—Length: 7 mm; width: 5 mm.        -   Sepal shape.—Ovate, base rounded, apex cuspidate.        -   Sepal surface.—Pubescent, many fine hairs 1 mm to 2 mm,            silver-gray 156D.        -   Sepal margin.—Entire.        -   Pedicel.—Length 14 mm, width 2 mm.        -   Pedicel surface.—Pubescent, many fine hairs 1 mm to 2 mm,            color 144A.-   Flowers:    -   -   Form.—Semi-double, initially cylindrical, becoming globose.        -   Flowering period.—Flowering commences in April and is            profuse until June; occasional flowers are produced until            July or September.        -   Fragrance.—None.        -   Flower retention.—Flowers are persistent.        -   Flower dimensions (including corolla tube).—5.5 cm to 6.0 cm            in diameter, 3.0 cm in depth.        -   Corolla tube dimensions.—2.5 cm in length; 0.5 cm to 1.0 cm            in diameter, narrowest at the base.        -   Petal arrangement.—Three whorls, each whorl consisting of 5            petals fused at base; inner whorl occasionally modified to            anther-bearing petaloid stamens.        -   Petal shape.—Widely ovate, base truncate, apex rounded.        -   Petal dimensions.—Outer whorl: 35 mm in length, 25 mm in            width. Second whorl: 28 mm in length, 22 mm in width. Inner            whorl: 25 mm in length, 20 mm in width.        -   Petal margin.—Smooth, gently ruffled.        -   Petals.—Color (both surfaces): White (whiter than NN155D),            base 150C. Spots: Occasionally present on adaxial surface as            short dashes towards petal base, length 1 mm to 2 mm, width            0.5 mm to 1.0 mm, color 150C. Surface: Smooth, glossy.        -   Venation.—Parallel, color 136A.        -   Peduncle.—Dimensions: 5 mm in length, 2 mm in width, ribbed.            Dimensions: Approximately 45 degrees from the stem. Surface:            Smooth. Color: N144D.-   Reproductive organs:    -   -   Petaloid stamens (when so modified).—1 to 9 in number,            length: 25 mm, width 20 mm, color white, (whiter than            NN155D).        -   Anthers.—Shape is oblong, bifid, length 3 mm, width 1.0 mm            to 1.5 mm, color 167D.        -   Pollen.—Absent.        -   Pistil.—One, length is 5 mm, diameter 0.5 mm, color 138C.        -   Style.—2.5 cm to 3.0 cm in length; initially light green            becoming white NN155D.        -   Stigma.—Color 137B; shape is rounded.        -   Ovary.—Ovate, 4 mm in length, 3 mm in diameter; surrounded            by dense very fine silver-gray hairs, length 5 mm, color            nearest 156D.-   Seed set: None observed.

COMPARISON WITH COMMERCIAL VARIETY

‘WALSNOWRUF’ may be compared with Azalea ‘Honesty’ (U.S. Plant Pat. No.12,054) which also bears double pure white flowers. ‘Honesty’ is aflorist or greenhouse azalea and is not hardy, whereas ‘WALSNOWRUF’ hasbeen observed to tolerate temperatures as low as −15° C. (USDA HardinessZone 7). In addition, the flowers of ‘Honesty’ are very large, up to 9cm in diameter, whereas the flowers of ‘WALSNOWRUF’ are typically 5.5 cmto 6.0 cm in diameter.

In addition, ‘WALSNOWRUF’ may be compared with Azalea ‘April Gem’(unpatented) which is a white double-flowered Mehlquist hardy hybrid.The flowers of ‘April Gem’ are borne singly or in clusters of 2 to 4flowers whereas the flowers of ‘WALSNOWRUF’ are arranged in largeclusters, typically between 8 and 12 flowers per inflorescence. Finally,the flowers of ‘April Gem’ are smaller (diameter 4 cm to 5 cm) than theflowers of ‘WALSNOWRUF’, and are generally described as slightlyfragrant whereas no fragrance has been observed in ‘WALSNOWRUF’.

I claim:
 1. A new and distinct variety of Rhododendron plant named‘WALSNOWRUF’ as described and illustrated herein.